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6'W x 2'D Perimeter Stormwater <br />Diversion Ditch <br />Composite Liner System <br />See Exhibit C for design details <br />and manufacturer specifications. <br />#5 <br />#4 <br />Final grade will be covered with a 6" of <br />recovered /reclaimed topsoil and /or imported <br />topsoil. This will be netted for erosion control and <br />re- vegetated. See Exhibit D for reclamation details. <br />Coarse Fraction Embankment <br />Face Grade = 1. 5h : I (33.7 °) <br />Barrier Impoundment (Drawing ES) <br />� <br />40 Leachate Collection Concrete Barrier <br />(see Drawing E12) <br />=11 I I III III1 I I I1 I I =1 I I I I III -111 Natural Grade <br />Earthen & Rock Backfill <br />Riprap Type L, D50 = 9 <br />Depth of 18 ", Hand Placed <br />2' Depth, 1:1 ; <br />i Side Slope �� <br />6' Bottom Channel Width <br />1 — — IV �— <br />Perimeter <br />Diversion Ditch <br />Scale: 1" = 2' <br />A trapezoidal channel with a bottom width of 6 feet, side slope of 1:1 and a <br />minimum clear depth of 2 feet will be constructed at each end of the <br />impoundment bench as it is raised, at the intersection with the natural grade, to <br />provide a permanent stormwater control. Type L riprap, sized nominally with a <br />median diameter of D50 =9 inches, shall be hand placed at a depth of 18 inches. <br />Rubble and /or slightly weathered stone sorted on -site from available material that <br />meets this size specification shall be acceptable for use. <br />This perimeter ditch will be constructed in phases as the impoundment expands. <br />Refer to Exhibit E Drawing E7 for the Phase 1 ditch and Drawing E 10 for Phase 2 <br />ditch. Interim diversion along the projected side slope line, prior to raising an <br />impoundment bench, shall be achieved by utilizing woven polypropylene sand <br />bags (nominally 14"x26" 50# capacity) stacked two bags wide as the first course <br />and one bag wide, centered, as the second course. The sandbags shall be removed <br />as permanent riprapped channel is installed. <br />Slimes Fraction Average <br />Impounded Grade = 2.1h : I (25.4 °) <br />r 601 -" 201 <br />Tailings Impoundment Cross - Section <br />Scale: 1" = 50' <br />/Stormwater &Sediment Collection <br />(see Drawing E13) <br />Composite Liner System: <br />The DRMS has determined that practice based ground water protection be applied to this operation through the implementation of a composite liner system <br />under the Tailings Impoundment. <br />Venture Resources has sought the expertise of Colorado Lining International in specifying the necessary geosynthetic products suitable for this application. A <br />three component system is specified consisting of a Geosynthetic Clay Liner (Bentomat DN), overlain with a textured 60 mil HDPE Geomembrane <br />impervious liner, overlain with a GeoComposite drainage layer. Specification sheets have been included as an appendix to this Exhibit C. Additionally, <br />extensive tailings geotechnical and interface testing has been conducted and this data can be found in Exhibit C. <br />Tailings Deposition: <br />The tailings leave the flotation plant at approximately 30% pulp density via a 2" double walled HDPE pipeline that gravity feeds down to the Tailings <br />Impoundment. The concrete leachate barrier provides for the first stage starter dyke for the tailings. Directly up- gradient of the concrete leachate barrier is a <br />small bowl that will be lined with a composite liner. This first stage has been named the Barrier Bench and can be seen in the drawing of Exhibit E5. <br />The tailings pipeline will cross along the top of concrete leachate barrier. Valved spigots are to be spaced at 20' intervals along the pipeline facing towards <br />the impoundment. These spigots may be variably pitched downward at an angle 20 ° -45° below horizontal. The spigot discharge rate and velocity can be <br />controlled by adjusting the valve. Deposition rates and classification density can be controlled by adjusting the spigot discharge angle. <br />Using this upstream method, an embankment begins to rise as the coarse fraction segregates and is deposited most closely to the point of discharge. The <br />slimes fraction flows on past this rising embankment and forms a beach that slopes gradually downward away from the point of discharge. Process water will <br />begin to pond at the toe of the beach slope as the tailings begin to settle, drain, and consolidate. This water is recycled back to the mill utilizing pumps. Care <br />must be taken to avoid allowing ponding water to encroach too closely to the embankment face, creating a high phreatic surface condition. <br />A beach width (LB, from embankment crest to ponded water) shall be maintained to achieve a ratio of LB /h > 5, where LB is beach width and h is <br />incremental embankment lift height (typically, h = 10 feet). Considering the permeability relationships between the coarse and slimes fractions (reported by <br />TRI in the geotechnical analysis attached in the appendix), this beach length ratio will provide for adequate control of the phreatic surface. This is acceptable, <br />according to Vick's Planning, Design, and Analysis of Tailings Dams, because this is the lowest allowable limit for this upstream method of impoundment P <br />over an impermeable liner foundation. 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